Can lateral assembly 'float' during deep cleaning?

[SplashDIY]

I recently took on my first deep clean of a Hayward S220T sand filter. (I never got to the point of substantially clear water overflowing the opening - calling it done after about 30 mins of gently moving a hose up/down/around).

I also gave the sand a detergent clean, using one of the degreasing compounds. History of this filter/age of sand is not documented.

During reassembly, I found that the multi-port valve could not be seated properly - the vertical pipe between multi-port and laterals assembly was now sitting too high in the filter body. I trimmed some of this thin-walled pipe off until I could obtain a good connection. Now, I find that initial back-pressure during routine filter flow is as low as 3 - 5 PSI. This suggests to me that the water flow is probably now bypassing the intended filtering circuit. Alas, I think I need to unload the filter, reseat a new lateral assembly and start over.

But before I take on this 'punishment repair' I thought I would run it by everyone here. Has anyone else had this issue? And can a lateral assembly really drift upwards a few inches through the surrounding sand, perhaps from spending too much time flushing the sand media with a hose?

 

[Texas Splash]

can a lateral assembly really drift upwards a few inches through the surrounding sand, perhaps from spending too much time flushing the sand media with a hose?

I don't recall hearing anyone say theirs lifted from the deep clean itself. It happens occasionally while lifting upwards to remove the MPV from the center pipe. It would seem unlikely to lift simply from the water underneath during the deep clean, but without any downward pressure from the MPV attached to the filter collar to keep everything in place, I wonder?

 

[SplashDIY]

Thanks for the ideas. I had a new replacement laterals assembly on hand in case I found the current one to be damaged. The original once removed all looked good, so I rebuilt the light-wall 1 ½" vertical ('riser') pipe with some Sched 40 and a coupler. By the way, if anyone else falls into this situation, the correct length from edge of laterals mounting flange to tip of riser pipe is 19 ½".

All is back in and running. This story still has another chapter to it - I am not seeing a back pressure during normal filtering of more than 5 PSI, even after running for 24 hours. But I'm in a tangle with this because I also have an (apparent) unresolved leak on a suction line. (the returns show continuous, large air bubbles being ejected). Guests arriving tomorrow morning, so I am going to set pump to run 24 hours per day and pray that there's no power interruption. (there's some effort needing in priming once the pump is stopped for more than a few minutes).

I wonder if entrained air hitting the filter could cause this kind of disruption (abnormally low back pressure)? For this filter set up (Hayward S220-T) I would previously see a newly back-washed and rinsed filter back pressure of around 10-12 PSI, and I would initiate a backwash once I had added about 5-6 PSI backpressure to that baseline.

 

[Texas Splash]

Maybe share some pics of your equipment pad from different angles so we can see everything?